Zero. The battery is sealed, armored, and designed to take impacts from things like a trailer hitch ball at highway speed, at least on Teslas. Other companies are going to have similar levels or hardening.
Now, will the rocks and stuff collect inside the rear bumper on a Model 3 because Tesla forget to install some plastic covers? Yeah, that might happen.
I wouldn’t even want to do that on my very solidly built '64 International C-900 pickup.
My experience with heat pumps in houses is that they aren’t good in Northern/colder climates, that they just can’t keep up in really cold weather. I understand that a car is not a house, it’s a lot smaller area to heat but then safety glass doesn’t have the insulating properties of triple-pane windows nor is metal the most insulating of materials. How well do the auto heat pumps work when the temps are negative? Are they able to work only because of the small cabin volume?
except for people dying due to self-driving mishaps.
I take your point, but this a very narrow point.
The Tesla Model S has a center of gravity 17.5” (44.5 cm) off the ground. My Subaru BRZ has a Cg 18.1” (46 cm) off the ground, so the difference is often quite small.
What’s more, sports cars often have a weight distribution of 50/50 (or very nearly so) to reap the handling benefits you mention. And for front-wheel drive cars, having the vast majority of the weight over the driven wheels is why they’re perceived as “good in snow.” Setting aside the question of tires, the percentage of weight over the driven wheels is nearly the sole determinant of whether a particular car is “good in snow.” (Tires are easily changed; weight distribution not so much).
Granted, my BRZ is a sports car and the Model S is a large sedan, so that’s a slightly unfair comparison. But it’s no more unfair than to say “EVs are safer than ICE vehicles” when you really mean that electric SUVs roll over less often than ICE SUVs. It’s true, but your phrasing was so broad that it perhaps diluted that truth.
It’s also true that without the volume of an ICE in front, you get a little more freedom to design effective crumple zones, but that’s not much of a constraint in reality; cars just got longer in front to make room for those zones.
It’s hard to make a valid blanket statement that EVs are safer or have better weight distribution than their ICE peers. What one can say is that EVs’ skateboard construction offers electric SUVs and sedans most of the handling and weight-distribution advantages previously enjoyed primarily by sports cars. These can improve safety, but they don’t necessarily do so.
Geothermal heat pumps seem to be the way to go, but that wouldn’t work very well on a car.
My Tesla Model 3 (Long Range version) even with battery weight is allegedly only 100 to 200 lb. heavier than my BMW 328, so I guess the weight question depends upon the car. The less expensive or smaller ICE cars will be substantially lighter. The point is that all this battery weight is filling an essentially fairly thick low floor pan, so the car’s center of gravity is very low, compared to any regular car with a huge metal chunk of engine and transmission higher up in the chassis. They perform spectacularly well in safety roll-over tests.
Heat pumps are most efficient when the temperature differential is the lowest. You are essentially pumping heat uphill from the low temperature to the higher one, so the less the hill the better. The one couple I knew who used a heat pump in super-cold northern Canada for their cottage, they threw a huge coil of piping into the lake, where even in winter it would be 4°C under the ice.
At least in terms of roll-over stability and weight transfer in corners, I think you also need to factor in track width of the vehicle. The BRZ has a higher cg working over a narrower track width (60.5" BRZ vs. 66.5" Model S)
On the family farm, we had wellhead gas from the 1940s untili recently. The gas company claims that it is now too high in hydrogen sulfide. My oldest brother worked for them and he bought his own test kit for hydrogen sulfide and found that the hydrogen sulfide in the gas is actually very low. That didn’t stop them from shutting off our access to the well and violating their contract.
So now I’m looking for an alternate (I have separate living quarters in town for the winter these days) and that looks like it will need to be a heat pump. I have plenty of room to put lines underground.
What I’d really like to do is to put in a large water tank about 10 to 20 feet below ground and use that for the heat pump, but I suspect that would be very expensive even if it would result in significant savings over just using outside air for the heat pump. I haven’t ruled it out, though.
What is a heat pump, please? And why is it relevant to the discussion? (Said the techno-peasant)
This is a heat pump:
They’re the most efficient way to heat/cool something like a house, but not really practical for something like a car. I’d consider this a joke, but a relevant, in-bounds joke (for what that’s worth).
In a car at higher temperatures, they should be reasonably efficient. When it is too cold, though, their efficiency can’t be that great.
My preference for cooling a house is a swamp cooler, but then where I live, the air is very dry.
This is a fair point. But it’s also easily quantified. My BRZ’s Cg is 3% higher than that of a Model S, and it’s track width is 10% narrower. Because roll moment scales linearly (force * distance) we can combine those terms and say that it takes an acceleration 13% greater to make a Model S roll over than it does my BRZ.
But because one must make room for wheels, tires, suspension travel and ground clearance, there’s a practical minimum for how low you can bring a car’s Cg.
Does anyone have numbers for the Model 3 sedan? I’d expect it’s Cg to be similar to the Model S and BRZ while its track is narrower than the Model S’s. Does anyone have a solid reference for the Model 3’s numbers?
Not likely at all. The batteries are VERY well protected.
A heat pump is more efficient than resistive heat? I thought heat pumps had resistive heater strips to make them heat better.
For a heat pump to work with outside air, it does need a second source of heat for really cold temperatures as the heat pump becomes more inefficient.
I don’t know if they would ever both be in use at the same time, but it does seem like it might be reasonable on a moderately cool morning to use the resistance heat to bring the temperature in the car up to something comfortable quicker. Even if they happened to do that, once heated, it wouldn’t make sense to keep anything but the heat pump running.
Heat pumps had, or perhaps have, heater strips in the duct work for very cold temperatures. That was some time ago, when I was in undergraduate school. I am not familiar with current practice.
Even my “geothermal” heat pump that I installed at my previous house had supplemental resistance heat. Things are usually engineered for a certain application, beyond which other measures need apply lest you over-engineer a thing.
I’ve heard of geothermal heat pumps that have several vertical pipes and ones that are buried horizontally. Is it pumping refrigerant or some other liquid that exchanges with the refrigerant?
In the country with at least a couple of acres, you would be more likely to run the lines horizontally. In the city where you have a city lot, they would need to be vertical.
There are other possibilities, too. One is to run the lines into a lake as long as the lake doesn’t dry up. Another would be to use groundwater from the aquifer – pump up groundwater, use it for the heat exchange, and drain back into the aquifer. Of course, you’d have to make sure that there was nothing to contaminate the water.
While not a heat pump, some people with swimming pools have been known to use the water from the swimming pool for their heat exchanger for their air conditioner system in the house. The cooler water from the swimming pool is closer to the desired temperature in the house and the heat exchanger helps heat up the water for the swimming pool.
One thing that I’ve considered is to bury a two or three thousand gallon tank on the farm about twenty feet deep, fill it up, and use that water in the heat exchanger. I’m not sure that would be enough and haven’t done the calculations.
In the summer when running the air conditioner, you are heating up the water as you cool the house. In the winter when running the heater, you are chilling the water as you heat the house. My problem is that it is very dry around here and in the summer, I prefer a swam cooler (evaporative cooler) in the house so if I had a heat pump but still used an evaporative cooler in the summer, I really wouldn’t heat the water back up in the summer.
I’ve been told that one problem with heat pumps is that people often don’t balance the use and so over time they are either cool the ground down or heat it up over a period of several years and make it less efficient. Has anyone else heard that? I’m not sure I believe it.
Most houses that are not on a city sewage line already have a large tank of er… fluid buried near their house. Perfect for heat pumps.